Zyrtec, Benadryl Among Common Drugs that Can Cause Dementia

bottles of Tylenol PM, Zyrtec, Xanax, and Immodium in front of red background; anticholinergic drugs that can cause dementia

Many drugs can cause brain fog and memory loss, but one type of drug can cause more severe conditions like dementia, stroke, and hallucinations. Anticholinergic drugs dampen neurotransmitters, sometimes causing permanent damage. 

How anticholinergic drugs work

Anticholinergic drugs block the neurotransmitter acetylcholine, which controls many bodily functions like involuntary muscle movement. 

Anticholinergics are most often used for urinary incontinence because they affect neurons which encourage muscle contraction, but they also influence physical capabilities and memory storage and retrieval. 

What makes these drugs even more dangerous is that many over-the-counter (OTC) drugs are considered anticholinergics or have anticholinergic effects. Many doctors don’t even warn patients that their medication may have severe consequences if taken for a long time. 

What conditions do anticholinergics treat?

Anticholinergics can be used to treat conditions like:

  • Allergies
  • Anxiety
  • Asthma
  • Chronic obstructive pulmonary disease (COPD)
  • Diarrhea
  • Gastrointestinal disorders
  • Insomnia
  • Motion sickness
  • Muscle spasms
  • Nausea and vomiting 
  • Parkinson’s disease
  • Psychiatric disorders
  • Urinary incontinence

List of anticholinergics

Anticholinergic drugs include medications like:

  • Amitriptyline (Elavil)
  • Benztropine (Cogentin)
  • Cyclobenzaprine (Amrix, Fexmid, Flexeril)
  • Diphenhydramine (Benadryl, Tylenol PM, et al.) 
  • Hydroxyzine (Atarax, Vistaril)
  • Olanzapine (Zyprexa)
  • Paroxetine (Brisdelle, Paxil)
  • Promethazine (Phenergan)

Other medications with less severe anticholinergic effects include:

  • Alprazolam (Xanax)
  • Cetirizine (Zyrtec)
  • Codeine
  • Furosemide (Lasix)
  • Loperamide (Imodium)
  • Loratadine (Alavert, Claritin)
  • Ranitidine (Zantac)
  • Tizanidine (Zanaflex)

A full list of anticholinergic drugs can be found here

Side effects of anticholinergics

Side effects of anticholinergics  include:

  • Dry mouth
  • Drowsiness
  • Blurry vision
  • Trouble urinating
  • Confusion
  • Hallucinations or delirium 
  • Constipation
  • Memory problems
  • Decreased sweating
  • Dementia


Harvard Medical School has linked prolonged use of anticholinergic drugs to dementia, especially in seniors. 

Anticholinergics also have the potential to cause:

  • Heat exhaustion,
  • Stroke, 
  • Overdose when taken with alcohol, and
  • The worsening of additional medical conditions. 

Note: Never stop taking your prescribed medication without first consulting your doctor. If you are concerned that your doctor has prescribed you a drug on this list, ask your pharmacist if it has any dangerous side effects with prolonged use. 

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